Freewheel arrangements used to couple a starter to an engine output shaft are known in practice. The known freewheel arrangements have a freewheel, wherein the freewheel has an inner ring, an outer ring and a plurality of wedging elements, in particular wedging rollers, between the inner ring and the outer ring. The wedging elements can each be moved from a wedging position, in which the wedging element prevents rotation of the outer ring relative to the inner ring in one circumferential direction, into a release position, in which the outer ring can be rotated in an opposite, second circumferential direction relative to the inner ring. In this case, the wedging elements are each preloaded into said wedging position by means of a spring element. In this case, helical springs are used as spring elements and are arranged together with the wedging elements within the wedging gap between the inner ring and the outer ring and are supported, on the one hand, on the associated wedging element and, on the other hand, on the outer or inner ring in order to bring about a preload of the wedging element into the wedging position in one circumferential direction. In order to allow integration of a freewheel of this kind into the drive train in a manner which saves installation space, freewheels have more recently been designed in such a way that they have a small axial overall length. This had the result of reducing the wedging gap between the inner ring and the outer ring in the axial direction and increasing it in the radial direction, the same applying in a corresponding manner to the wedging element within the wedging gap. In a corresponding way, it was also necessary to reduce the turn diameter of the helical springs used as a spring element. However, a helical spring made smaller in this way leads to the problem that reliable support for the wedging element on the helical spring, on the one hand, and reliable support for the helical spring on the inner ring or outer ring, on the other hand, is not assured without expensive measures for the reliable attachment and guidance of the helical spring at both ends. In other words, either reliable operation of the spring element designed as a helical spring is jeopardized or the production and assembly of the freewheel is associated with an increased outlay.
It is therefore an object of the present invention to provide a freewheel having at least one wedging element and a spring element associated with the wedging element to preload the wedging element into the wedging position thereof, which freewheel ensures reliable operation of the spring element and is associated with a low production and assembly outlay. The present invention is furthermore based on the object of providing a freewheel arrangement for a motor vehicle having a freewheel with such advantages.
The freewheel according to the invention has an inner ring, an outer ring and at least one wedging element between the inner ring and the outer ring. Here, the free space formed in the radial direction between the outer ring and the inner ring for accommodating the wedging element can also be referred to as the wedging gap. The wedging element can be a wedging roller, a wedging body or a locking blade, for example. Although the term wedging element or at least one wedging element is used herein in all cases, it is preferred if a plurality of wedging elements is arranged between the inner ring and the outer ring, these preferably being spaced apart uniformly from one another in the circumferential direction. The wedging element can be moved from a wedging position, in which the wedging element prevents rotation of the outer ring relative to the inner ring in one circumferential direction, into a release position, in which the outer ring can be rotated or turned in an opposite, second circumferential direction relative to the inner ring. The individual wedging element is preloaded into the abovementioned wedging position by means of a spring element. As with a helical spring, the spring element of the freewheel according to the invention also has an elongate spring body. However, the elongate spring body is not wound in a helical shape; on the contrary, the elongate spring body extends in a radial plane, i.e. in a plane defined by the radial directions of the freewheel, wherein the elongate spring body has a corrugated profile in the radial direction. Thus, the elongate spring body can have an undulating or zigzag profile in the radial direction, for example, wherein the elongate spring body extends in the radial plane in this arrangement. Since the elongate spring body extends in the radial plane, it is particularly suitable for use within a wedging gap which has a particularly small extent or width in relation to the axial direction. Thanks to the elongate spring body of the spring element extending in the radial plane, it is consequently possible to provide a freewheel with a particularly small axial overall length. Moreover, the corrugated profile in the radial direction of the elongate spring body means that the spring element can have a significantly greater extent in the radial direction than in the axial direction. Consequently, a spring element of this kind is suited for extension over a large part of the height or substantially over the entire height of the wedging gap in the radial direction and thus for filling the wedging gap to a great extent. This has the advantage that a wedging element designed to correspond to the wedging gap can be supported in a particularly reliable manner on the spring element without the need to take further measures in this regard, as is the case, for example, with a spring element designed as a helical spring, which has the same extent in the axial direction and in the radial direction and is consequently not suited to filling the height of a relatively narrow wedging gap. The attachment or support of the spring element to or on the outer or inner ring is thereby simplified.
In a preferred embodiment of the freewheel according to the invention, the spring body is formed by a sheet-metal part or wire. The sheet-metal part can be formed by a sheet-metal strip which has a corrugated profile in the radial direction, for example, wherein, in this case, the direction of the width of the sheet-metal strip preferably corresponds to the axial direction of the freewheel. The wire can have a circular cross section, for example, making it possible to resort to a standardized or simple wire in the manufacture of the spring element, which reduces the outlay on manufacture.
In an advantageous embodiment of the freewheel according to the invention, the corrugated profile of the spring body in the radial direction means that it has radially outer corrugation peaks and radially inner corrugation troughs, between which legs of the spring body extend, said legs preferably extending in a straight line. In this embodiment, it is furthermore preferred if at least two, if appropriate at least three, corrugation peaks and at least two, if appropriate at least three, corrugation troughs are provided.
In another preferred embodiment of the freewheel according to the invention, the spring body has a supporting leg on which the wedging element can be supported or is supported. The supporting leg is preferably designed as the last or end leg of the spring body corrugated in the radial direction. It is also preferred if the supporting leg extends over at least 50% of the height of the wedging element in the radial direction.
In order to achieve reliable support of the wedging element on the supporting leg of the spring body, the supporting leg in another advantageous embodiment of the freewheel according to the invention has a greater width in relation to the axial direction than another section, if appropriate than at least one of the legs, of the spring body. If the spring body legs extending between the corrugation peaks and corrugation troughs have a narrower width than the supporting legs in relation to the axial direction, not only is reliable support of the wedging elements on the supporting leg ensured but, what is more, what may be a desirable, lower spring stiffness or spring rate of the spring element can be ensured by the spring body legs which have a reduced width.
In order, on the one hand, to ensure reliable support of the wedging elements on the supporting leg and, on the other hand, to bring about uniform introduction of the preloading force of the spring element into the wedging element, the supporting leg has a profile which is matched to the outer contour of the wedging element. Thus, depending on the design of the outer contour of the wedging element, the supporting leg can have a curved, bent or kinked profile, for example. In the case of a wedging element designed as a wedging roller, a profile of the supporting leg in the form of a circular arc matched to the circular outer contour of the wedging roller is preferred.
In another advantageous embodiment of the freewheel according to the invention, the profile of the supporting leg is matched to the outer contour of the wedging element in such a way that, when viewed in the axial direction, the outer contour of the wedging element can be supported or is supported on the supporting leg at least in a linear manner or at at least two mutually spaced points in order to ensure reliable support and a relatively uniform introduction of the preloading force of the spring element.
In order to improve the support of the wedging element on the supporting leg and force transmission between the wedging element and the spring element and, in particular, to avoid tilting of the spring element, the supporting leg can be supported or is supported, on the one hand, by means of a connecting section, which can form a corrugation peak or corrugation trough for example, between the supporting leg and an adjacent leg of the spring body and, on the other hand, at at least one further point of support on the adjacent leg of the spring body.
Based on the embodiment described above, the supporting leg and the adjacent leg of the spring body in another advantageous embodiment of the freewheel according to the invention are designed in such a way that the supporting leg is capable of being supported at the further point of support by transferring the wedging element from the wedging position into the release position. In other words, the support for the supporting leg at the further point of support on the adjacent leg of the spring body is accomplished only by transferring the wedging element from the wedging position into the release position. As an alternative, the supporting leg and the adjacent leg of the spring body can be designed in such a way that the supporting leg is continuously supported at the further point of support. Thus, the supporting leg and the adjacent leg of the spring body can be fastened to one another at the further point of support for example, welding or soldering being suitable fastening methods for example. However, continuous support can also be effected by preloading the spring element in the wedging position of the wedging element in such a way that the supporting leg is already supported at the further point of support on the adjacent leg of the spring body in the wedging position of the wedging element.
In order to achieve the intended support or capacity for support at the further point of support on the adjacent leg of the spring body, the supporting leg has a section which projects in the direction of the adjacent leg, by means of which the supporting leg can be supported or is supported at the further point of support. The section which projects in the direction of the adjacent leg can be implemented merely by the supporting leg having the above-described profile matched to the outer contour of the wedging element, which is bent, curved or kinked if appropriate. As an alternative, the section of the supporting leg which projects in the direction of the adjacent leg can be formed by a free end section of the supporting leg, which allows the intended support irrespective of the supporting leg profile matched to the outer contour of the wedging element. It is also possible for the free end section to be supported at the further point of support by transferring the wedging element into the release position or for it to be continuously supported at the further point of support, as has already been explained above.
In order, on the one hand, to achieve accurate positioning of the spring element within the wedging gap and, on the other hand, to ensure a largely undisturbed action of the spring element, at least one shoulder projecting in an axial direction, by means of which the spring body can be supported or is supported in this axial direction, is provided on the spring body in a particularly preferred embodiment of the freewheel according to the invention. Support by means of the shoulder projecting in the axial direction can be provided, for example, on a side wall delimiting the wedging gap in this axial direction. The shoulder projecting in the axial direction has the advantage that the spring body is not supported or not capable of being supported over its entire side facing in the axial direction on the side wall or the like, with the result that the operation of the spring body or the spring element, i.e. the imposition and relief of the load, is largely unaffected, while the support or capacity for support in the axial direction by means of the projecting shoulder nevertheless allows accurate positioning of the spring body or of the spring element in the axial direction within the wedging gap.
In principle, the shoulder projecting in the axial direction for the purpose of support in or allowing support in this axial direction could be produced in any way, e.g. by attaching a distance piece to the spring body. In another preferred embodiment of the freewheel according to the invention, however, the at least one projecting shoulder is formed by a section of the spring body which is widened in relation to the axial direction. If the spring body is formed by a sheet-metal part or sheet-metal strip for example, the sheet-metal part or sheet-metal strip would have a section which was wider than another section in order to obtain the shoulder projecting in the axial direction. If the spring body is formed by a wire which has a circular cross section, the projecting shoulder could be produced by upsetting the cross section in the radial direction and thus by widening the cross section in the axial direction. In both cases mentioned, the projecting shoulder would consequently be formed in one piece with the spring body or formed by a section of the spring body.
In another advantageous embodiment of the freewheel according to the invention, the at least one projecting shoulder is arranged in the region of the corrugation peaks and/or corrugation troughs in order to provide support or a capacity for support for the spring body or the spring element in the axial direction in a manner which is particularly tilt-proof.
According to another advantageous embodiment of the freewheel according to the invention, both shoulders projecting in one axial direction and shoulders projecting in the opposite axial direction are provided on the spring body.
In another preferred embodiment of the freewheel according to the invention, at least three shoulders projecting in one axial direction are provided in order to provide tilt-proof support. It is preferred here if the at least three shoulders projecting in one axial direction are arranged at the corners of an imaginary triangle in order to achieve the abovementioned security against tilting and reliable support for the spring body or the spring element. In this embodiment too, it is preferred if three shoulders projecting in one axial direction and three shoulders projecting in the opposite axial direction are provided on the spring body.
In order to provide relatively small contact areas with a side wall or the like delimiting the wedging gap by means of the shoulders projecting in the axial direction, the shoulders projecting in the axial direction in another advantageous embodiment of the freewheel according to the invention are of rounded, pointed and/or tapered design at the end thereof pointing in this axial direction.
In order to ensure accurate positioning of the spring body within the wedging gap between the inner ring and the outer ring, the spring body in another preferred embodiment of the freewheel according to the invention can be supported or is supported resiliently in the axial direction, wherein this resilient support or capacity for resilient support in the axial direction can be provided on a side wall or the like delimiting the wedging gap in the axial direction, for example. Thus, for example, the abovementioned projecting shoulders can be designed to be resilient in the axial direction.
In a particularly advantageous embodiment of the freewheel according to the invention, at least one elastic supporting tongue is provided on the spring body, by means of which tongue the spring body can be supported or is supported resiliently in the axial direction. The supporting tongue can be arranged in the region of a corrugation peak or corrugation trough, for example. However, it has proven advantageous if said supporting tongue is provided on one of the legs of the spring body which extends between a corrugation trough and a corrugation peak. In this embodiment, it is furthermore preferred if the spring body can be supported or is supported resiliently in the axial direction over an extended area by the supporting tongue.
In another advantageous embodiment of the freewheel according to the invention, the supporting tongue is formed in one piece with the spring body.
In another advantageous embodiment of the freewheel according to the invention, the spring body is arranged on the freewheel with a preload on the supporting tongue, with the result that the spring body is preloaded into its axial position within the wedging gap.
In another preferred embodiment of the freewheel according to the invention, the spring body can be supported or is supported resiliently both in one axial direction and in the other axial direction. For this purpose, it is preferred if at least two supporting tongues are provided, of which one supporting tongue resiliently supports the spring body in one axial direction while the other supporting tongue resiliently supports the spring body in the other, opposite axial direction.
In another preferred embodiment of the freewheel according to the invention, the spring body is provided at least partially with a wear-inhibiting coating. It is preferred here if the corrugation peak, that is to say at least one of the corrugation peaks, the corrugation trough, that is to say at least one of the corrugation troughs, the supporting leg, the projecting shoulder and/or the supporting tongue have/has a coating, especially since said components may be subject to increased frictional wear, which can be counteracted in this way. The coating is preferably designed as a carbon layer, if appropriate as an amorphous carbon layer, that is to say as a “DLC coating” in order to reduce wear to a large extent.
In another advantageous embodiment of the freewheel according to the invention, the spring body has a fastening section for the direct or indirect fastening of the spring body on the inner or outer ring. Thus, the spring body could, for example, be fastened directly on the inner or outer ring by means of the fastening section or could be fastened indirectly thereon by means of a side wall connected for conjoint rotation to the inner or outer ring and intended to delimit the wedging gap in the axial direction.
In another preferred embodiment of the freewheel according to the invention, the fastening section is fastened by a latching action on the inner or outer ring in order, on the one hand, to achieve reliable fastening of the spring body and, on the other hand, to provide simple mounting of the spring body on the inner or outer ring by means of the fastening section. In this embodiment too, fastening on the inner or outer ring can be accomplished directly or indirectly. In this embodiment, it is furthermore preferred if the spring body is fastened directly or indirectly on the inner or outer ring in a captive manner by means of the fastening section in order to further simplify the mounting of the spring bodies. In this context, captive fastening means that the spring body is fastened directly or indirectly on the inner or outer ring in a captive manner even before the wedging elements and/or the other ring of the inner or outer ring has/have been fitted.
In order to ensure reliable fastening of the spring body on the inner or outer ring by means of the fastening section of the spring body, the fastening section in another preferred embodiment of the freewheel according to the invention has a greater width in relation to the axial direction than another section, if appropriate than at least one of the legs, of the spring body.
In another advantageous embodiment of the freewheel according to the invention, the fastening section of the spring body is fastened on a fastening projection, behind which the fastening section engages, if appropriate with a wedging or latching action, on both sides in relation to the mutually opposite circumferential directions. The fastening projection can, for example, be provided on the outer ring and project inward into the wedging gap in a radial direction. As an alternative, the fastening projection can also be provided on the inner ring and project outward into the wedging gap in a radial direction, although the abovementioned variant embodiment having a fastening projection on the outer ring is preferred.
In another advantageous embodiment of the freewheel according to the invention, the fastening section engages behind the fastening projection from the inside and/or from the outside in relation to the radial direction. If the fastening section engages behind the fastening projection in a radial direction both from the inside and from the outside, particularly reliable retention and, if appropriate, captive arrangement and fastening of the spring body on the fastening projection by means of the fastening section is possible.
In another advantageous embodiment of the freewheel according to the invention, a side wall secured for conjoint rotation on the inner ring or outer ring is provided, serving to delimit a wedging gap between the inner ring and the outer ring in the axial direction. Since this is a side wall secured for conjoint rotation on the inner ring or outer ring, this is not formed integrally or in one piece with the inner ring or outer ring, which simplifies the production of the freewheel.
In another particularly preferred embodiment of the freewheel according to the invention, the fastening projection on which the fastening section of the spring body is fastened is provided on the side wall for delimiting the wedging gap between the inner ring and the outer ring in the axial direction. Thus, in this embodiment, it is possible to dispense with a fastening projection on the inner or outer ring, while a corresponding fastening projection on the side wall is simpler to produce, thus simplifying the production of the freewheel. Moreover, a fastening projection provided on the side wall makes it possible to provide a fastening projection which is spaced apart from the inward-facing side of the outer ring and the outward-facing side of the inner ring and behind which the fastening section of the spring body can thus engage in a relatively simple manner in respect of the mutually opposite circumferential directions and the mutually opposite radial directions.
In another preferred embodiment of the freewheel according to the invention, the fastening projection provided on the side wall is formed by a side wall section projecting into the wedging gap between the inner ring and the outer ring. In other words, the fastening projection is formed integrally or in one piece with the side wall. An integral fastening projection of this kind can be produced in a relatively simple manner, especially if the side wall is of thin-walled design and/or is formed by a sheet-metal part. Thus, it has proven advantageous if the integral fastening projection is formed by a bent, punched-out and/or tongue-shaped section of the side wall in order to reduce the outlay on manufacture and nevertheless to ensure reliable fastening of the spring body on the fastening projection by means of its fastening section.
In order to dispense with a fastening projection, in particular on the outer ring, on the inner ring or on the side wall, and thus to reduce the overall weight of the freewheel, the fastening section of the spring body in another particularly advantageous embodiment of the freewheel according to the invention is introduced into a fastening depression, directly or indirectly fastening the spring body to the inner or outer ring. Even if the term fastening depression is consistently used herein, the term can also include fastening apertures or fastening openings. In each case, it is advantageous with this embodiment if the fastening section is introduced into the fastening depression with a latching action and/or in a captive manner, as already explained above. In this embodiment, the fastening depression is preferably provided in the inner side of the outer ring, the side facing toward the inner ring, or in the outer side of the inner ring, the side facing toward the outer ring. As an alternative, the fastening depression could also be provided in the abovementioned side wall for delimiting the wedging gap between the inner ring and the outer ring in the axial direction, in which case the fastening section could protrude in one of the axial directions into the fastening depression in the side wall, for example.
In order to fasten the spring body reliably on the respective component of the freewheel by means of the fastening section, the fastening depression in another advantageous embodiment of the freewheel according to the invention has an opening edge, behind which the fastening section of the spring body can engage or does engage. In this embodiment, the fastening section of the spring body is preferably in the form of a clip in order to allow the latching fastening already mentioned above of the fastening section of the spring body within the fastening depression.
In another preferred embodiment of the freewheel according to the invention, the wedging element is designed as a wedging roller. In this context, the term wedging rollers should be taken to mean wedging elements with a circular periphery or a circular outer contour.
Since the advantages, mentioned at the outset, of the spring element having an elongate spring body which extends in a radial plane and has a corrugated profile in the radial direction are significant particularly in the case of freewheels which have a wedging gap that is narrow in the axial direction and high in the radial direction and has correspondingly dimensioned wedging elements, the ratio of a width to an outside diameter of the wedging roller in another preferred embodiment of the freewheel according to the invention is equal to or less than 1:3, preferably equal to or less than 1:4, particularly preferably equal to or less than 1:5.
In another advantageous embodiment of the freewheel according to the invention, the outer side of the inner ring, the side facing toward the wedging element, the wedging roller if appropriate, is of substantially circular design, while the inner side of the outer ring, the side facing toward the wedging element, the wedging roller if appropriate, has a shape which differs from a circle. A wedging gap which tapers in phases in the circumferential direction is thereby achieved, with the result that the wedging element prevents rotation of the outer ring relative to the inner ring in the first circumferential direction, when the wedging element or the wedging roller is in the wedging position, while the outer ring can rotate relative to the inner ring in the second circumferential direction in the release position of the wedging element or the wedging roller.
The freewheel arrangement according to the invention for a motor vehicle has a freewheel of the type according to the invention. Moreover, the freewheel arrangement has a starter ring, which is connected for conjoint rotation to the inner ring, a drive output side, that is to say, for example, a drive output side of an internal combustion engine, which is connected for conjoint rotation to the outer ring, and a starter, which is in continuous rotary driving engagement with the starter ring.
In a preferred embodiment of the freewheel arrangement according to the invention, the inner ring is supported directly or indirectly in the radial direction on the drive output side or on a fixed housing in a manner which allows rotation, if appropriate via a rolling contact or sliding contact bearing, with the result that the starter is decoupled from the rotary motion of the drive output side after starting by means of the starter, even if the starter is in continuous rotary driving engagement with the starter ring.
In a particularly preferred embodiment of the freewheel arrangement according to the invention, the freewheel is designed as a dry freewheel or as a wet freewheel. In the case of embodiment as a dry freewheel, no lubricant is thus provided between the inner ring and the outer ring, on the one hand, and the wedging elements, on the other.